Measurement of energy flux at the substrate in a magnetron sputter system using an integrated sensor

Knowledge of the energy flux in a sputter deposition system is important for predicting and controlling the properties of the growing film. The use of discrete sensors such as thermocouples for heat measurement has a potential contact problem due to the temperature jump between the surface of the wall and the surrounding gas especially at very low pressures. Embedded sensors such as a microfabricated polysilicon thin film thermistor eliminates the problem associated with thermal connection. In this study, the fabricated sensor is calibrated using ohmic self-heating before the deposition plasma is switched on, and also after the plasma is switched off (passive mode). At low pressures (up to 20 mTorr), pressure has an insignificant effect on the thermal resistance of the sensor. For substrate temperatures up to 250 °C, the sensor response is linear with input power. For a 3 in magnetron system, values of steady state energy flux measured with the sensor range from 5 to $46 mW/cm2$ for aluminum (Al) and 14 to $114 mW/cm2$ for copper (Cu) depending on the process conditions. These values compare well with those determined theoretically. Magnetron power was varied between 75 and 300 W, gas pressure 5–10 mTorr, and substrate–target distance 10.8–21 cm.